1. Field of Use
The present invention relates to semiconductor circuits and more particularly to bipolar array circuits including control apparatus therefor.
2. Prior Art
In order to improve the cost performance ratios of LSI computer systems, designers have begun to make more extensive use of gate array technology. A gate array generally consists of a large number of basic circuit elements such as AND/NAND gates or flip-flops. The array is customized by final metallization layers that interconnect the basic circuit elements in the desired fashion. For further information regarding gate array, reference may be made to the article "Customized Metal Layers Vary Standard Gate Chip" by Johoshua Pomeranz, et al. in the Mar. 15, 1979 issue of the publication "Electronics" and in the article "Semicustom Technology Drives Minicomputer Architecture" by David Cane in the December 1980 issue of the publication "Computer Design".
In such array, it has been found that the propagation delays of such gate array circuits can vary so as to affect the performance of the computer system in which they are employed. This can be due to differences occurring during fabrication as well as changes in circuit resistor tolerances occurring during operation.
In general, a variety of techniques have been employed to compensate for variations in process parameters on an LSI chip. Examples of such techniques are disclosed in U.S. Pat. Nos. 3,609,414 and 3,970,875. Since these techniques compensate for variations in threshold gate voltage of field effect transistors (FETS) on an LSI chip, they are not particularly applicable to bipolar circuits and more particularly to gate array circuits.
Accordingly, it is an object of the present invention to provide apparatus for controlling the propogation delay of the basic circuits within a gate array so as to overcome the effects of variations in process parameters.
It is a further object of the present invention to provide apparatus for controlling the operational delays in an gate array so as to be uniform notwithstanding variations in fabrication and environmental conditions.